Flowmeters may measure the rate of flow of a fluid in a pipe or other pathway. The fluid may be, for example, a gas or a liquid, and may be compressible or incompressible. One type of flowmeter is a vortex flowmeter which measures parameters including, for example, flow rate based on the principle of vortex shedding. Vortex shedding refers to a natural process in which a fluid passing a bluff body (sometimes referred to as a shedder) causes a boundary layer of slowly moving fluid to be formed along the surface of the bluff body. A low pressure area is created behind the bluff body and causes the boundary layer to roll up, which generates vortices in succession on opposite sides of the bluff body. The vortices induce pressure variations that may be sensed by a pressure sensor. The vortex-shedding pressure variations have a frequency that is related to the flow rate. Accordingly, by measuring the frequency of the pressure variations, the flow rate may be determined.
Vortex flowmeters provide vortex frequency data that can be used in conjunction with flow calibration factors to determine the velocity and volumetric flow rate of the fluid passing through the meter. With inputted fluid density values, the mass flow rate can also be computed. These measurements, and others, can be transmitted to a control room or other receiver over a communication line, such as, for example, a standard two-wire 4-20 milliamp (“mA”) transmission line.
In some applications (e.g., in the petroleum, mining, chemical, and waste industries), the fluid flow monitored by a vortex flowmeter may sometimes include paraffin or other low-temperature melting point hydrocarbons, bentonite or other clays, lipids, or other similar materials that can form deposits in certain conditions.
The present inventors have developed systems and methods, described in detail below, that improve the ability operate a vortex flowmeter with fluids that contain materials that may form deposits on components of the flowmeter.